Fix installation of cxxabi.h through libc++.

Previously, the install command for the cxxabi headers specified
the wrong component, and therefore they were not being included
in the install-cxx command.

This patch corrects the component name.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@318989 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed